JP7306079B2 - Liquid ejector - Google Patents

Description

The present invention relates to a liquid ejection device.

When a coating area on an object to be coated, for example, a rectangular coating area measuring about 200 mm long and about 1,000 mm wide is coated by a liquid ejection head that is held on an XY drive table, the dots of paint ejected from the liquid ejection head are It is placed on the object to be coated at regular intervals in both the vertical and horizontal directions. FIG. 6 shows an example of an enlarged dot group placed on an object to be coated. The nozzle diameter is 0.15 mm, the speed of the nozzle in the X direction is 640 m/s, the distance between the surface to be coated and the liquid ejection head is 10 mm, the dot diameter is 2.0 mm, and the dot spacing is 0.2 mm. As a result, 5,000 dots per row are printed in the X direction to cover approximately 1,000 mm (1,002 mm to be exact). On the other hand, one row of 1,000 dots is printed in the Y direction to cover approximately 200 mm (202 mm to be exact). Therefore, a painting area of about 200 mm×about 1,000 mm is covered by arranging 5,000×1,000=5×10 6 dots.

In the X direction, a nozzle head mounted on an XY drive table moves left and right at a constant speed, and dots are ejected when it enters the target coating area. The liquid ejection head is moved by moving the XY table along the Y axis so that dots are arranged at intervals of 0.2 mm in the Y direction as well. The above is the conventional coating method using the liquid ejection head.

However, the conventional coating method described above has the following problems. This will be described with reference to FIG. As shown in FIG. 7( a ), dot groups 102 appearing as thin vertical lines at the left and right ends of the painting area 101 appear to protrude from the painting area 101 . When this is magnified with a microscope, as shown in FIG. 7B, the dot group 102 is formed by small dots with a diameter of about 100 μm existing so as to protrude from the target coating area 101. and to the right of the last dot in left-to-right strokes, and to the left of the last dot in right-to-left strokes. The existence of the protruding dots is an unnecessary existence as noise, contrary to the desire for a paint area with a clear parting.

Here, the cause of generation of such noise dots will be described. The mechanism by which paint dots are ejected from the nozzles of the liquid ejection head is described, for example, on pages 151 to 154 of Non-Patent Document 1. Further detailed observation using a strobe microscope or the like reveals that the liquid Changes over time in paint (ink) dots ejected from the nozzles of the ejection head are as shown in FIGS. 8(a) to 8(e). Here, FIG. 8 shows the process of forming dots, FIG. 8(a) is a cross-sectional view of the nozzle showing the state before ejection, and FIG. 8(b) is a cross-sectional view of the nozzle showing the state immediately after ejection. 8(c) is a diagram showing the state in which the paint dots are separated into parent dots and satellite dots from the state of FIG. 8(b), and FIG. 8(d) is the state after a predetermined time has elapsed from the state of FIG. 8(c). FIG. 8E is a diagram showing a state in which the parent dot has landed and the satellite dot is flying.

I will explain each one. When the tip of the nozzle 2N is filled with paint (FIG. 8(a)), pressure is applied from behind to eject the paint as paint dots 2a. Then, at the moment the paint dot 2a is discharged, the tail portion of the paint dot 2a is pulled backward by the viscosity and surface tension of the paint 20 in the tip of the nozzle 2N, forming a sharp cone shape (FIG. 8(b)). . The paint on the bottom portion separates from the dot on the body portion (parent dot 2b) to form a small dot 2c. This small dot 2c is called a "satellite dot" (Fig. 8(c)). The falling speed of the satellite dot 2c becomes slower than the falling speed of the parent dot 2b because the rear portion is pulled backward. At the moment when the parent dot 2b falls on the coating area 101 on the object to be coated 100 and spreads flat, the satellite dot 2c still exists in the air (Fig. 8(d)) and then falls on the parent dot 2b (Fig. 8 (e)).

In actual painting, the liquid ejection head moves in the X direction, for example, to the right at a constant speed. Therefore, as shown in FIG. As can be seen from the vector area velocity, the ink lands on the right side of the parent dot 2b. When the nozzle 2N moves to the left, the ink lands with a shift to the left. The satellite dots 2c become noise dots that protrude from the left and right ends of the painting area.

For example, when paint is discharged from a nozzle with a diameter of 0.15 mm that moves at a constant speed of 640 mm/s in the x direction, the vertical drop speed of the parent dot 2b is 5,850 mm/s, and the vertical drop speed of the satellite dot 2c is 4,850 mm/s. At 300 mm/s, the diameter of the parent dot 2b that landed on the object 100 10 mm below was 2.0 mm, and the diameter of the satellite dot 2c was 0.1 mm. Observed at a distance of 0.4 mm.

By the way, Japanese Patent Laid-Open No. 2002-200012 discloses one method for solving the satellite dot problem described above. The inkjet printing method disclosed in US Pat. No. 6,200,002 positions an inkjet printhead having a large number of nozzles adjacent to a sheet of print medium, and moves the sheet or printhead along a scanning axis to perform printing. Ink droplets (satellite dots) are ejected from one of the nozzles in an ejection direction that is offset from the direction perpendicular to the scan axis such that the main and tail portions of the ink droplets strike the same location on the media sheet. Select parameters and speed of scanning.

Edited by Tsuyoshi Iwamoto and Kodera, "Series Advanced Display Technology 8, Digital Hardcopy Technology," Kyoritsu Shuppan Co., Ltd., November 2000, p. 151-154

Japanese Patent No. 4210014

However, the method disclosed in Patent Document 1 assumes that the center of the outlet hole defines the normal axis with respect to the inlet and outlet holes of the orifice of the nozzle, and the center of the inlet hole is offset from the normal axis by an offset amount. There is the disadvantage that a dedicated nozzle is required because of the need to

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to improve image quality by controlling the ejection of paint dots.

In order to solve the above-mentioned problems, the invention according to claim 1 is a liquid discharge head held on an XY table, which is moved in the XY directions and discharges paint at equal intervals to perform coating. A coating method using a liquid ejection head that eliminates noise caused by satellite dots landing at a position separated by a distance d in the movement direction of the ink jet nozzle from the end of the last dot of the ink jet nozzle, wherein the liquid ejection head is For a predetermined dot line painted by ejecting paint at equal intervals while moving in the direction of , the liquid is ejected so as to overlap the dot line and at the same interval as the dot line. A liquid ejection head is used, characterized in that the ejection head is moved in the opposite direction, and the center position of the first dot that moves in the opposite direction is separated from the center of the last dot toward the satellite dot by a distance d or more. To provide a painting method.

In order to solve the above-mentioned problems, the invention according to claim 2 provides a liquid ejection head held on an XY table, which is moved in the XY directions and ejects paint at equal intervals to perform coating. A coating method using a liquid ejection head that eliminates noise caused by satellite dots landing at a position separated by a distance d in the movement direction of the ink jet nozzle from the end of the last dot of the ink jet nozzle, wherein the liquid ejection head is With respect to a predetermined dot row coated by ejecting paint at equal intervals while moving in the direction of , the dot is moved to a position perpendicular to the moving direction of the ink jet nozzle by a predetermined pitch interval p. The liquid ejection head is moved in the opposite direction so that the paint is ejected at the same interval as the rows, and is moved in the opposite direction, where r is the radius of the main dots ejected from the inkjet nozzle onto the surface to be coated. Provided is a coating method using a liquid ejection head, characterized in that the center position of the first dot is separated from the center of the last dot toward the satellite dot by at least the distance calculated based on the following formula (1). do.

・・・（１）

... (1)

According to the present invention, image quality can be improved by controlling the ejection of paint dots.

1 is a configuration diagram showing an embodiment of an inkjet printing apparatus using a liquid ejection head; FIG. FIG. 4 is a block diagram illustrating one embodiment of a controller; BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows 1st embodiment of the coating method which concerns on this invention. It is an explanatory view showing a second embodiment of the coating method according to the present invention. FIG. 11 is an explanatory diagram showing the dot shift amount in the coating method according to the second embodiment; FIG. 4 is an enlarged view showing paint dot groups; (a) is a diagram showing a state in which the dot group appears to protrude from the painted area, and (b) is an enlarged diagram showing the protruding portion from the state of the dot group. 2 shows the process of forming dots, (a) is a cross-sectional view of the nozzle showing the state before ejection, (b) is a cross-sectional view of the nozzle showing the state immediately after ejection, and (c) is the paint from the state of (b). (d) is a diagram showing a state after a predetermined time has elapsed from the state of (c), and (e) is a diagram showing a state in which a parent dot has landed and a satellite dot has been formed. It is a figure which shows the state which is in flight. FIG. 4 is an explanatory diagram showing directions of impact of parent dots and satellite dots;

Hereinafter, a coating method using a liquid ejection head according to the present invention will be described in detail based on a preferred embodiment with reference to the drawings. First, an embodiment of an inkjet printing apparatus used to carry out a coating method using a liquid ejection head according to the present invention will be described.

[Configuration of Inkjet Printing Device]
As shown in FIG. 1, an inkjet printing apparatus (hereinafter simply referred to as "printing apparatus") 1 equipped with a liquid ejection head has a liquid ejection head (hereinafter simply referred to as "printing apparatus") that ejects paint dots toward a coating area 101 of an object 100 to be coated. 2, an X-axis moving mechanism 3 for reciprocating the nozzle head 2 in the X-axis direction, and a mechanism for holding the X-axis moving mechanism 3 and reciprocating the nozzle head 2 in the Y-axis direction. a pair of Y-axis moving mechanisms 4, 4, an XY table frame 5 that supports both ends of the Y-axis moving mechanisms 4, 4 to hold them at a predetermined height, and a paint supply device 6 that supplies paint to the nozzle head 2 and a controller 7 for controlling the nozzle head 2, the X-axis moving mechanism 3, and the Y-axis moving mechanisms 4, 4 (XY table) according to the contents of coating. Here, the inkjet printing apparatus 1 is an example of a "liquid ejecting apparatus".

The nozzle head 2 is moved in the XY directions on the surface of the coating area 101 of the object 100 by the X-axis moving mechanism 3 and the Y-axis moving mechanisms 4, 4. A coating film is formed on a coating region 101 by discharging dots of paint from a nozzle toward a coating region 101, which is a surface to be coated.

FIG. 2 is a block diagram illustrating one embodiment of a controller. The controller 7 is mainly composed of a computer (PC) 70 that controls the printing apparatus 1 according to a stored program and a PLC (programmable logic controller) 71 that performs control operations in a predetermined order by the computer 70. The computer (PC) ) 70 is connected to a keyboard 72 used for various input operations and a nozzle control circuit 73 for controlling the driving of the nozzle head 2 . A nozzle drive circuit 74 for driving the nozzle head 2 under the control of the nozzle control circuit 73 is connected to the nozzle control circuit 73 .

In addition, the PLC 71, which operates based on the computer 70 and the nozzle control circuit 73, has a touch panel display 75 that displays various displays and enables various input operations by touching the screen, the X-axis movement mechanism 3, and the Y-axis movement mechanism 3. It comprises a motor controller 76 that controls drive motors (not shown) for the axis moving mechanisms 4 and 4, and a motor drive circuit 77 that drives the drive motors under the control of the motor controller 76. .

If the painting area 101 is about 200 mm×about 1,000 mm, the painting will be covered by 5,000×1,000=5×10 6 dots arranged as described above. In this case, the nozzle head 2 mounted on the X-axis moving mechanism 3 moves left and right at a constant speed in the X direction, and dots are ejected when it enters the target coating area. In the Y direction, the nozzle head 2 is moved by driving the Y-axis moving mechanisms 4, 4 so that dots are arranged at intervals of 0.2 mm.

The computer 70 controls the PLC 71 and the nozzle control circuit 73 according to a pre-stored program, and drives the X-axis moving mechanism 3 and the Y-axis moving mechanisms 4, 4 to move the nozzle head 2 in a predetermined print pattern. do. At that time, the paint dots discharged from the nozzle head 2 are discharged onto the object 100 to be coated at equal intervals in both the vertical and horizontal directions.

Next, a coating method using the liquid ejection head according to the present invention will be described. First, the coating method according to the first embodiment will be described.

[Coating method according to the first embodiment]
In the painting method according to the first embodiment, when the dot rows are struck from right to left at the same interval (pitch) so as to overlap one dot row that is struck from left to right, the right By shifting the center position of the dot to the left from the center position of the dot to the right from the center position of the dot to the right by the distance d or more from the edge of the dot to the right to the satellite dot , which makes the satellite dots invisible. A detailed description will be given below with reference to FIG.

FIG. 3 is an explanatory diagram showing the first embodiment of the coating method according to the present invention. In the figure, RS is the first dot of a predetermined dot row struck from left to right, RL is the last dot, and SR is the satellite dot of the last dot RL. Also, LS is the first dot of the dot row struck from right to left, LL is the last dot, and SL is the satellite dot of the last dot LL.

As shown in FIG. 3, if the distance from the right end of the last dot RL in the dot line printed from left to right to the satellite dot SR is d, then the center position of the dot printed from right to left is from left to right. The satellite dot SR becomes invisible if the center position of the dot to be shot to the right is shifted to the right by d or more. That is, if the center position of the first dot LS printed from right to left is shifted to the right by d or more from the center position of the last dot RL printed from left to right, the satellite dot RS will be printed from right to left. It becomes invisible because it is incorporated into the first dot LS that is displayed. Since the center position of the last dot LL printed from right to left is shifted to the right by d or more from the center position of the first dot RS printed from left to right, the satellite dot SL is printed from left to right. The satellite dot SL becomes invisible because it lands on the first dot RS of the dropped dot row.

For such control, a control program for controlling the PLC 71, the nozzle control circuit 73, and the motor controller 76 is installed in the computer (PC) 70 in advance so that the above distance d is generated, and the nozzle head 2 is operated according to this control program. The motor controller 76 controls the operations of the X-axis moving mechanism 3 and the Y-axis moving mechanisms 4, 4 of the XY table to move the table at an optimum speed. can be achieved by

Further, in this embodiment, the distance when the recording head is moved at a predetermined speed is photographed by a camera (not shown) or the like, and the controller specifies the distance d based on the photographed image and stores it in a storage unit (not shown). can be done. Also, when moving the print head at a speed different from the predetermined speed, the controller can vary the distance d based on the predetermined speed and the speed of the print head.

[Effect of the first embodiment]
According to the coating method using the liquid ejection head according to the first embodiment, the nozzle head 2 is moved in a predetermined direction and the paint is ejected at equal intervals to the predetermined dot line that is coated. The nozzle head 2 is moved in the opposite direction so as to overlap the dot line and eject the paint at the same interval as the dot line, and the center position of the first dot that moves in the opposite direction is shifted from the center of the last dot. Since the distance d or more is set to the satellite dot side, it is possible to realize a clean parting end face free from noise dots while using the normal nozzle head 2 without making the nozzle head 2 into a special shape. It has the effect of being able to

In this embodiment, the ejection is performed while moving the head held by the XY table in the XY directions, but the present invention is not limited to this. The head may be fixed and the ejection target may be moved in the XY directions, or both the head and the ejection target may be moved. Alternatively, the liquid may be ejected while moving the head in the YZ direction or the XZ direction.

[Coating method according to the second embodiment]
Next, a coating method according to the second embodiment will be described. FIG. 4 is an explanatory diagram showing the first embodiment of the coating method according to the present invention. As in FIG. 3, RS is the first dot in a row of dots printed from left to right, RL is the last dot, SR is the satellite dot of the last dot RL, and LS is printed from right to left. The first dot in the dot row, LL is also the last dot, and SL is the satellite dot of the last dot LL. However, the first dot LS to the last dot LL in the dot line printed from right to left is shifted from the first dot RS to the last dot RL in the dot line printed from left to right by a predetermined pitch interval p in the Y direction. has fallen to In the painting method according to the second embodiment, when a dot row is struck from right to left at the same interval as the upper dot row, with a predetermined pitch interval below a prescribed dot row struck from left to right. , where d is the distance from the end of the last dot in a given dot row to its satellite dot, r is the radius of the dot, and p is the pitch interval, dots are struck from right to left as shown in FIG. The satellite dots are made invisible by shifting the center position of the dot from the center position of the dot struck from left to right by the distance calculated by the formula (1) or more.

・・・（１）
図５を参照しつつさらに説明する。

... (1)
Further description will be made with reference to FIG.

FIG. 5 is an explanatory diagram showing the dot shift amount in the painting method according to the second embodiment, where r is the dot radius, p is the pitch interval, and d is the distance from the right edge of the last dot RL to the satellite dot SR. is.

As shown in FIG. 5, by shifting the center position of the first dot LS printed from right to left from the center position of the last dot RL printed from left to right by (d+d') or more, the satellite dot SR is It overlaps the first dot LS of the dot row struck from right to left, and the satellite dot SR disappears. However, d' is calculated by the following equation (2).

・・・（２）

... (2)

For example, when r = 1.0 mm and p = 0.2 mm, d' = 0.02 mm, and the center position of dots printed from right to left is (d + d'), that is, 0.4 + 0.02 mm. = 0.42 mm to the right.

Here, referring to FIG. 5, the process of calculating the above d' by the formula (3) will be described.

・・・（３）

... (3)

For such control, a control program for controlling the PLC 71, the nozzle control circuit 73, and the motor controller 76 is installed in the computer (PC) 70 in advance so that the above distance d is generated, as in the first embodiment. According to this control program, the motor controller 76 controls the operations of the X-axis moving mechanism 3 and the Y-axis moving mechanisms 4, 4 of the XY table to move the nozzle head 2 at an optimum speed and pitch. can be achieved by controlling the ejection timing and ejection amount of the paint.

[Effect of Second Embodiment]
According to the coating method using the liquid ejection head according to the second embodiment, for a predetermined dot row coated by ejection from the nozzle head 2, a predetermined The nozzle head 2 is moved in the opposite direction so that the paint is ejected at the same interval as the dot row to the position moved by the pitch interval p, and the radius of the main dots ejected from the nozzle head 2 onto the surface to be coated is r. In this case, the center position of the first dot that moves in the opposite direction is moved from the center of the last dot to the satellite dot side by a distance greater than or equal to the distance calculated based on the value shown by the following formula (1). There is an effect that it is possible to realize a clean parting end face free from noise dots while using a normal specification nozzle head 2 without making the nozzle head 2 into a special shape.

・・・（１）

... (1)

The present invention is not limited to the above embodiments, and various modifications are possible without departing from or changing the technical idea of the present invention.

1 Inkjet printing device (an example of a liquid ejection device)
2 nozzle head 2a paint dot 2b parent dot 2c satellite dot (small dot)
3 X-axis movement mechanism 4 Y-axis movement mechanism 5 XY table frame 6 Paint supply device 7 Controller 20 Paint 70 Computer (PC)
71 PLC
72 keyboard 73 nozzle control circuit 74 nozzle drive circuit 75 touch panel display 76 motor controller 77 motor drive circuit

Claims (4)

a head for ejecting liquid onto an ejection target;
a moving mechanism for moving at least one of the object to be discharged or the head;
moving the ejection target or the head in the predetermined direction so that the ejection target or the head overlaps the dot row formed by ejecting the liquid while moving the ejection target or the head in the predetermined direction; a controller that moves the center position of the dot ejected first when moving in the opposite direction by a distance d or more from the center position of the last dot when moving in the predetermined direction;
a camera that captures an image that can be used to identify the movement distance of the ejection target or the head when the ejection target or the head is moved at a predetermined speed;
a storage unit that stores the distance d specified by the controller based on the image captured by the camera;
has
The distance d is the distance from the end of the last dot in the dot row formed by ejecting the liquid while moving the ejection object or the head in the predetermined direction to the satellite dot. is the distance and
The liquid ejection device , wherein the controller moves the distance d or more obtained by referring to the storage unit . a head for ejecting liquid onto an ejection target;
a moving mechanism for moving at least one of the object to be discharged or the head;
A predetermined pitch interval p in a direction perpendicular to the movement direction of the ejection target or the head with respect to dot rows formed by ejecting liquid while moving the ejection target or the head in a predetermined direction moving the object to be ejected or the head in a direction opposite to the predetermined direction so as to eject the liquid to the position moved by 1, and let r be the radius of the main dot ejected from the head to the object to be ejected , Let distance d be the distance from the end of the last dot in the dot row formed by ejecting the liquid while moving the ejection object or the head in the predetermined direction to the satellite dot on the predetermined direction side. In this case, the center position of the dot ejected first when moving in the opposite direction is the distance calculated based on the following formula (1) from the center position of the last dot when moving in the predetermined direction. a controller that moves more than
a camera that captures an image that can be used to identify the movement distance of the ejection target or the head when the ejection target or the head is moved at a predetermined speed;
a storage unit that stores the distance d specified by the controller based on the image captured by the camera;
has
The liquid ejection device , wherein the controller moves the distance d or more obtained by referring to the storage unit .

... (1) The controller is
causing the head to eject the liquid at predetermined intervals while moving the ejection target or the head in the predetermined direction;
3. The liquid ejecting apparatus according to claim 1, wherein the liquid is ejected from the head at the predetermined intervals while moving the object to be ejected or the head in the opposite direction. The controller is
4. The center position of the dot ejected first when moving in the opposite direction is moved from the center position of the last dot when moving in the predetermined direction to the satellite dot side by the distance d or more. The liquid ejection device according to any one of 1.

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